The Association Between Intrahepatic Cholestasis Of Pregnancy And Fetal Growth Restriction

Background: Fetal growth restriction means that fetal growth unable to reach the genetically determined growth potential.Fetal growth restriction is clinically defined as a birth weight less than the tenth percentile or two standard deviation of birth weight of the same gestational age and the same sex.Fetal growth restriction is one of the major causes of perinatal morbidity and mortality which seriously influences and delays the development of intelligence and physical fitness in childhood and adolescence and which is closely related to adult health.Therefore,to investigate the etiology and pathogenesis of fetal growth restriction,and to prevent and control the occurrence of fetal growth restriction which is of great significance for reducing the perinatal mortality and improving the quality of our population.In recent years,the association between pregnancy complications such as intrahepatic cholestasis of pregnancy and adverse perinatal outcomes has been increasingly emphasized by experts in obstetrics.The increase of serum total bile acid level is the most sensitive and specific index for the diagnosis of ICP.It is also the standard for mild and severe discrimination of ICP.Studies had shown that ICP could lead to premature birth,fetal distress,meconium stained amniotic fluid,and even sudden stillbirth and other adverse perinatal outcomes.But whether ICP will increase the risk of FGR and LBW remains controversial.And,there was no a large sample cohort study with correlation between the risk of ICP and FGR.The mechanism of how ICP causes FGR during pregnancy is poorly understood.Objective and significance: The purpose of this study was divided into two parts:(1)A large sample cohort study was conducted to investigate whether there was an association between ICP and FGR and its association strength;(2)The association among ICP ? impaired placental development caused by placental oxidative stress and inflammation and FGR was verified by a case-control study.After the completion of this study,there will be a certain correlation between ICP and FGR,and further elucidate that the mechanism of ICP induced FGR may be caused by maternal inflammation and impaired placental development.This study not only has the important meaning to reduce our perinatal neonatal morbidity and mortality,improve population quality,but also it may provide a new theoretical basis for the further study of the damage effects and mechanisms of which ICP induced embryonic and fetal development,and for the establishment of reasonable prevention and treatment strategies.Methods: A retrospective cohort study was conducted in the first part of this study.All pregnant women who were hospitalized and delivered in the First Affiliated Hospital of Anhui Medical University from January 1th to December 31 th,2013 were analyzed.Finally,pregnant women with complete birth records? laboratory indicators and live births were enrolled as birth cohort.The following three studies were carried out:(1)The associations among maternal serum TBA level and neonatal birth weight,birth length,head circumference and chest circumference;(2)To study the strength of association between ICP and LBW;(3)To study strength of the association between ICP and FGR.The second part of this study was a case-control study.A total of 60 ICP patients(30 mild ICP,30 severe ICP)and 30 controls were enrolled in the First Affiliated Hospital of Anhui Medical University from January 1th to June 30 th,2016.The blood and placenta tissue samples of the subjects were taken in strict accordance with the principle of informed consent.Professional staff collected fasting blood samples of ICP before treatment and the control group,separated serum,and then stored them in the-80? refrigerator.After the delivery,took a piece of placenta tissue and put it into 10% Formaldehyde Solution,then embed it in paraffin.The serum TBA level was measured by enzyme cycle method.The levels of serum TNF-?,IL-8 and IL-10 were measured by ELISA.Placental Nrf2,3-NT,Ki67,PCNA,and CD34 among three groups were detected by immunohistochemistry.The following two aspects of research were carried out:(1)Association of ICP with placental development: placental Nrf2,3-NT,Ki67,PCNA,and CD34 were compared among three groups;(2)Association of ICP with maternal inflammatory response: the levels of serum TNF-?,IL-8 and IL-10 in mild,severe ICP and controls were compared.Results: The first part of the retrospective cohort analysis: a total of 2527 pregnant women who delivered to live singleton from Obstetrics Department in the First Affiliated Hospital of Anhui Medical University from January 1 to December 31,2013 was reviewed.The demographic characteristics and neonatal sex were analyzed as follows: 2289 pregnant women below 35 years of age accounted for 90.58% of the subjects.Pregnant women with normal pre-pregnant weight(the pre-pregnant BMI ranging from 18.5 to 23.9)were 70.28%(1776/527).Pregnant women who family economy were the low income(monthly per capita income of less than 2000 yuan)were 7.24%(183/2527),median household income(per capita income of 2000-4000 yuan)were 68.74%(1737/2527),and high income(monthly per capita income above 4000 yuan)were 24.02%(607/527).The mean gestational age was 38.6±2.3(mean±SD)weeks.The incidence of preterm birth(gestational age less than 37 weeks)was 12.47%(315/2527).Primiparous pregnant women were 80.97%(2046/2527)in this cohort.In addition,1327 were boys and 1200 were girls in the newborns.The ratio of male to female was 110.6: 100.Serum TBA levels were measured before delivery.Maternal serum TBA levels and neonatal birth weight related studies showed that maternal serum TBA levels were negatively correlated with neonatal birth weight,and the linear correlation coefficient was-0.289(P<0.001).The relationship between serum TBA levels and birth weight was then analyzed according to the gender of the newborns.It was found that maternal serum TBA levels were negatively correlated with boy birth weight,and the linear correlation coefficient was-0.295(P<0.001),and negatively correlated with birth weight of female infants,the linear correlation coefficient was-0.285(P<0.001).Linear correlations between serum TBA levels among pregnant women and neonatal birth length,head circumference and chest circumference were further studied.Our results showed that the maternal serum TBA level among pregnant women and neonatal birth length,head circumference and chest circumference were negatively correlated,which the correlation coefficients were-0.210(P<0.001),-0.234(P<0.001),-0.254(P<0.001),respectively.The present study showed that 10.51%(243/2311)LBW infants were observed among subjects without ICP and 29.17%(63/216)among with ICP.The relative risk for LBW was 3.58(95%CI: 2.60,4.94)among subjects with ICP.The intensity of correlation between ICP and LBW was further analyzed using Binary Logistic regression model.Our results showed that the unadjusted relative odds ratio for LBW was 3.55(95%CI: 2.57,4.90)among subjects with ICP.After adjust pre-pregnancy body mass index,pregnant women age,parity,and gestational weeks,OR for LBW was 3.84(95%CI: 2.38,6.20)among subjects with ICP.After adjusted maternal serum ALT and AST,OR for LBW was 2.31(95%CI: 1.61,3.30)among subjects with ICP.The association between ICP and FGR also was analyzed.These results showed that the incidence of FGR was 6.84%(158/2311)among subjects without ICP and 22.69%(49/216)among subjects with ICP.The relative risk for FGR was 4.00(95%CI: 2.80,5.71)among subjects with ICP.The intensity of correlation between ICP and FGR was further analyzed using Binary Logistic regression model.As expect,the unadjusted relative odds ratio for FGR was 4.05(95%CI: 2.83,5.79)among subjects with ICP. After adjust pre-pregnancy body mass index,pregnant women age,parity,and gestational weeks,OR for FGR was 3.50(95%CI: 2.41,5.10)among subjects with ICP.After adjusted maternal serum ALT and AST,OR for FGR was 3.35(95%CI: 2.25,4.99)among subjects with ICP.In the second part of this study,a case-control study was conducted to investigate the association between ICP and placental oxidative stress and inflammation,and the association between ICP and maternal inflammatory response.The present study found that there was no significant difference on placental CD34 in the vascular endothelial cells of the fetal side among control,mild ICP and severe ICP groups.Further study found that placental PCNA and Ki67,two markers of the proliferating activity,were higher expression in trophoblast in control group than in mild and severe ICP groups.Placental 3-NT positivity is a marker of protein oxidation and nitration.The expression and distribution of placental 3-NT in the control group and the ICP group were examined in the present study.These results showed that 3-NT was highest expressed in the cytoplasm of placental trophoblast cells in the severe ICP group.The expression was lower in mild group and lowest in the control group.Nrf2 is an oxidative inhibitory protein.Its negative is a marker of oxidative stress.The expression and distribution of placental Nrf2 in the control group and the ICP group were detected in the present study.Our results found that Nrf2 was highest expressed in the nucleus of placental trophoblast cells in the control group.The expression was lower in mild than severe group and lowest in the severe group.In addition,maternal inflammation during pregnancy is one of the important causes of FGR.TNF-?,a proinflammatory cytokine,IL-8,a chemokine,and cytokine IL-10,an anti-inflammatory cytokine in maternal serum were measured in the present study.Our results found that maternal serum TNF-? level in the mild and severe ICP group were significantly higher than that in the control group.However,there was no significant difference between mild and severe ICP group.Maternal serum IL-8 level in the mild and severe ICP group was significantly higher than that in the control group.Moreover,the level in the severe group was significantly higher than that in the mild group.Maternal serum IL-10 level in the mild and severe ICP group was significantly lower than that in the control group.There was no significant difference between mild and severe group.Conclusion: Maternal serum TBA level was negatively correlated with neonatal birth weight,birth length,head circumference and chest circumference.Intrahepatic cholestasis of pregnancy not only elevates the risk of low birth weight but also increases fetal growth restriction,which may be associated with the damage of placental development caused by inflammation and oxidative stress and maternal inflammatory response.